Microstructure evolution of compressed micropillars investigated by in situ HR-EBSD analysis and dislocation density simulations

Zoller, Kolja; Kalácska, Szilvia; Ispánovity, Péter Dusán; Schulz, Katrin

doi:10.5802/crphys.55

Cited by 12 publications

(10 citation statements)

References 77 publications

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“…The density of geometrically necessary dislocations (GNDs) is not to be mistaken with the average density of mobile dislocations involved in Orowan's equation (ρ) (see Hirth and Lothe, 1982;Zoller et al, 2021). The later would be the sum of the GND and the statistically stored dislocations (SSDs), which includes loops, dipoles, or multipoles, if they are mobile and not locked into the crystal (e.g., by impuri-ties).…”

Section: Geometrically Necessary Dislocation Densitiesmentioning

confidence: 99%

Dislocation and disclination densities in experimentally deformed polycrystalline olivine

Demouchy

Thieme²,

Barou³

et al. 2023

Eur. J. Mineral.

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Abstract. We report a comprehensive data set characterizing and quantifying the geometrically necessary dislocation (GND) density in the crystallographic frame (ραc) and disclination density (ρθ) in fine-grained polycrystalline olivine deformed in uniaxial compression or torsion, at 1000 and 1200 ∘C, under a confining pressure of 300 MPa. Finite strains range from 0.11 up to 8.6 %, and stresses reach up to 1073 MPa. The data set is a selection of 19 electron backscatter diffraction maps acquired with conventional angular resolution (0.5∘) but at high spatial resolution (step size ranging between 0.05 and 0.1 µm). Thanks to analytical improvement for data acquisition and treatment, notably with the use of ATEX (Analysis Tools for Electron and X-ray diffraction) software, we report the spatial distribution of both GND and disclination densities. Areas with the highest GND densities define sub-grain boundaries. The type of GND densities involved also indicates that most olivine sub-grain boundaries have a mixed character. Moreover, the strategy for visualization also permits identifying minor GND that is not well organized as sub-grain boundaries yet. A low-temperature and high-stress sample displays a higher but less organized GND density than in a sample deformed at high temperature for a similar finite strain, grain size, and identical strain rate, confirming the action of dislocation creep in these samples, even for micrometric grains (2 µm). Furthermore, disclination dipoles along grain boundaries are identified in every undeformed and deformed electron backscatter diffraction (EBSD) map, mostly at the junction of a grain boundary with a sub-grain but also along sub-grain boundaries and at sub-grain boundary tips. Nevertheless, for the range of experimental parameters investigated, there is no notable correlation of the disclination density with stress, strain, or temperature. However, a broad positive correlation between average disclination density and average GND density per grain is found, confirming their similar role as defects producing intragranular misorientation. Furthermore, a broad negative correlation between the disclination density and the grain size or perimeter is found, providing a first rule of thumb on the distribution of disclinations. Field dislocation and disclination mechanics (FDDM) of the elastic fields due to experimentally measured dislocations and disclinations (e.g., strains/rotations and stresses) provides further evidence of the interplay between both types of defects. At last, our results also support that disclinations act as a plastic deformation mechanism, by allowing rotation of a very small crystal volume.

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Section: Geometrically Necessary Dislocation Densitiesmentioning

confidence: 99%

Dislocation and disclination densities in experimentally deformed polycrystalline olivine

Demouchy

Thieme²,

Barou³

et al. 2023

Eur. J. Mineral.

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“…To characterize the type and sign of the dislocation at a given point of the scanned surface the method introduced in Ref. [36] is followed, that is, the quantity…”

Section: Burgers Vector Analysismentioning

confidence: 99%

“…can be calculated where the index i goes through all the six Burgers vectors existing in the FCC crystal [36]. Certainly, one cannot determine the relative population of the different types of dislocations from B, but according to the definition given by Eq.…”

Section: Burgers Vector Analysismentioning

confidence: 99%

Statistical properties of fractal type dislocation cell structures

Lipcsei

Kalácska

Ispánovity

et al. 2023

Phys. Rev. Materials

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“…Here it is subdivided into a Lomer density ρ ξ lom and a stabilized dislocation density ρ ξ S . An overview is given in Zoller et al [54]. However, in DDD, it is not trivial to get this exact information about the different types of densities.…”

Section: Dislocation Density Based Modelmentioning

confidence: 99%

Identification of dislocation reaction kinetics in complex dislocation networks for continuum modelling using data-driven methods

Katzer

Zoller

Weygand

et al. 2022

Journal of the Mechanics and Physics of Solids

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Microstructure evolution of compressed micropillars investigated by in situ HR-EBSD analysis and dislocation density simulations

Abstract: Microstructure evolution of compressed micropillars investigated by in situ HR-EBSD analysis and dislocation density simulations

Cited by 12 publications

References 77 publications

Dislocation and disclination densities in experimentally deformed polycrystalline olivine

Dislocation and disclination densities in experimentally deformed polycrystalline olivine

Statistical properties of fractal type dislocation cell structures

Identification of dislocation reaction kinetics in complex dislocation networks for continuum modelling using data-driven methods

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